The movie's producer told People that the actress insisted to him that she "really wanted to get serious".
"She said, 'I'm committed, I'm not going to be late. I'm really, really excitied about doing this and working with these other actors'," Harper said. "So we're excitied."
He added that he believes Lohan is "going to be phenomenal" in the film and that he is not "worried whatsoever".
The Other Side is expected to start shooting in October off the coast of Massachusetts. Jason Lee, Woody Harrelson, Giovanni Ribisi, Alanis Morissette and Dave Matthews will also star in the movie.